This application relates to the art of processing lens blanks and, more particularly, to fining and polishing apparatus used in processing lens blanks.
The invention is particularly applicable to processing of lenses having compound curvatures, such as toric lenses, and will be described with particular reference thereto. However, it will be appreciated that certain features of the invention have broader aspects and may be used in processing other lenses.
Toric lenses and the like are processed with fining and polishing apparatus having a pair of downwardly extending pins on the spindle pressure arm for reception in a pair of corresponding recesses in the upper face of a lens block. A generally horizontal line extending through both pins provides a reference axis for maintaining the lens blank in a desired rotated orientation during fining and polishing operations. Due to the compound motion of the lap, along with its curvature, the lens block and lens blank assembly tilts and wobbles about the pins on the spindle pressure arm during the fining and polishing operations. The use of two pins has been considered necessary for holding the lens blank against rotation and in proper alignment so that curves will not be ground off axis from the desired prescription. However, the use of two pins inhibits tilting of the lens and the lens block in a vertical plane passing through the two pins. This causes unequal loading on the lens blank and can result in incomplete fining or polishing at certain places on the lens blank, optical distortions, and thin edges. These problems may be reduced to acceptable levels by using large rigid lens blocks which occupy substantially the entire rear surface area of a lens blank to minimize deflection of such blank. The use of large lens blocks does not allow contour edging of the lens blank while the same lens block remains attached to the lens blank and it would be desirable to have a mounting arrangement which could be used with small lens blocks while minimizing distortions in the lens blank.
Accordingly, it has been considered desirable to develop a new and improved adapter arrangement for holding a lens block and associated lens blank during a fining and polishing process. The subject invention meets these needs, successfully overcomes the above noted problems and others, and is readily adapted to use in a variety of applications.